Quantum path selection in high-order harmonic generation from aligned molecules

Abstract

We theoretically investigate high-order harmonic generation (HHG) from aligned N(2) molecules with a driving field composed of two-color circularly polarized laser pulses. It is shown that the combination of N(2) molecules and the waveform-controlled laser field allows us to select either long or short quantum path, depending on molecular alignment angles, while in atom Ar, two paths show comparable contribution to HHG. The selection of single quantum path in aligned N(2) molecules leads to an ultrabroad and smooth XUV supercontinuum, giving rise to isolated attosecond pulses generation. Moreover, we can control the intensity ratio of two attosecond pulses by adjusting the molecular alignment angles, providing an opportunity for attosecond pump-probe technique.

Broadband-Isolated Attosecond Pulse Generation by Two-Color Elliptically Polarized Laser Pulses

“…[24] Quantum path selection was also investigated from aligned N 2 molecules by two-color circularly polarized laser pulses. [25,26] In our previous work, [7] we discussed IAP generated from two-color circular pulses, and found that the quantum paths can be controlled despite the ''gating'' structure disappearing. In this article, we discuss the HHG and IAP generation by combining two-color elliptically polarized laser pulses, and find that the short quantum is controlled and only long quantum path contributes to the HHG.…”

Generation of non-integer high-order harmonics and significant enhancement of harmonic intensity*

“…[29] Both odd and even harmonics could be obtained by breaking the symmetry of the system, such as using two-color field or multi-color field, [30][31][32][33] adding chirped field, [34] employing inhomogeneous field [35] to break the symmetry of the laser field, or using complex molecular systems to break the symmetry of the target. [36] The appearance of 3n ± 1 order harmonic pairs is achieved by the action of targets and twocolor counter-rotating circularly polarized laser fields. [37][38][39] Selection rules for atomic and molecular systems under the N-fold symmetries field radiation were also explored.…”

Quantum Path Selection and Isolated-Attosecond-Pulse Generation of H 2 + with an Intense Laser Pulse and a Static Field

“…For instance, Bandrauk et al [13] have presented the timefrequency profile analysis and the evolution of nuclear wave packets to identify electron recollision times responsible for the generation of attosecond pulse trains. By taking advantage of the alignment dependence of HHG in N 2 molecules, Yao et al [14] obtained isolated pulses by constructing a driving laser field with a rapidly varying waveform. In this Letter, we propose a method to generate an isolated pulse by adding a static field to a fundamental pulse.…”